US businesses are poised to invest billions of dollars into Northern Ireland if the “Windsor” deal on post-Brexit trading arrangements leads to political stability in the region.

The investment is described as ready-to-go by people with knowledge of the plans, following months of talks led by UK Northern Ireland Secretary Chris Heaton-Harris. However, UK and US officials familiar with the matter said money is only likely to start flowing once the political crisis there has ended. This may require the DUP backing the Windsor deal, and ultimately ending the political standoff at Stormont, Northern Ireland’s legislative assembly.

The prospect of significant international investment would be a carrot for UK Prime Minister Rishi Sunak to dangle in front of Northern Irish unionists as he attempts to convince them to back the agreement.

The Democratic Unionist Party has blocked the formation of a power-sharing government for more than a year in an ongoing protest at the terms of the original Brexit deal. The party says it will take time to decide whether it will back the new UK-EU agreement and resume power-sharing. 

The potential for significant external investment in Northern Ireland is likely to add to pressure on the DUP to support the deal.

The money on offer would help the Northern Irish defense industry and science sector, among others, and provide a major boost to its economy, according to UK government officials. US companies are interested in investing in the region, some of them working in conjunction with Northern Irish universities, a US official said.

Speaking on Tuesday morning, Sunak said Northern Ireland’s “unique” access to both the UK internal market and the EU’s single market was attractive to overseas investors. 

“It’s like the world’s most exciting economic zone,” Sunak said, claiming companies from the US were “queuing up” to invest in the region. “They keep talking about it, saying: When are you gonna get this thing sorted because we’ve got all these ideas, we’ve got investment that we want to bring.”

Responding to the announcement of the Windsor deal on Monday, US President Joe Biden said in a statement: “I am confident the people and businesses of Northern Ireland will be able to take full advantage of the economic opportunities created by this stability and certainty, and the United States stands ready to support the region’s vast economic potential.”

In January, Heaton-Harris met the new US special envoy to Northern Ireland, Joe Kennedy - whose brief is primarily economic — and discussed “how to continue attracting US investment,” according to a statement from the UK government. Heaton-Harris also visited Washington D.C., Boston and New York to drum up investment opportunities, his office said.